OFDMA (Orthogonal Frequency Division Multiplexing Access) is a downlink multiple access technology used by an LTE (Long Term Evolution, Long Term Evolution) system.
In an LTE system, a PDCCH (Physical Downlink Control Channel, physical downlink control channel) is used to allocate uplink and downlink resources to a UE (User Equipment, user equipment). For use of a PUCCH (Physical Uplink Control Channel, physical uplink control channel) format (format) 1a or 1b (which may also be represented as PUCCH format 1a/1b), a PUCCH format 1a or 1b resource number is related to the first CCE (Control Channel Element, control channel element) occupied by a corresponding PDCCH.
UE-specific reference signals can be used to demodulate a PDSCH and an R-PDCCH. For antenna ports 7-14, a reference signal sequence is defined as
            r      ⁡              (        m        )              =                            1                      2                          ⁢                  (                      1            -                          2              ·                              c                ⁡                                  (                                      2                    ⁢                    m                                    )                                                              )                    +              j        ⁢                  1                      2                          ⁢                  (                      1            -                          2              ·                              c                ⁡                                  (                                                            2                      ⁢                      m                                        +                    1                                    )                                                              )                      ,          ⁢      m    =          {                                                                  0                ,                1                ,                …                ⁢                                                                  ,                                                      12                    ⁢                                          N                      RB                                              max                        ,                        DL                                                                              -                  1                                                                                    normal                ⁢                                                                  ⁢                cyclic                ⁢                                                                  ⁢                prefix                                                                                        0                ,                1                ,                …                ⁢                                                                  ,                                                      16                    ⁢                                          N                      RB                                              max                        ,                        DL                                                                              -                  1                                                                                    extended                ⁢                                                                                          ⁢                                                                                        ⁢                cyclic                ⁢                                                                  ⁢                prefix                                                    ,            where c(i) is a quasi-random sequence, NRBmax,DL is the maximum system bandwidth, which equals 110. The quasi-random sequence c(i) is initialized as cinit=(└ns/2┘+1)·(2NIDcell+1)·216+nSCID, where ns is a timeslot number, NIDcell is a cell ID, and nSCID is a scrambling ID.
Because a PDCCH is mapped to several OFDM (Orthogonal Frequency Division Multiplexing) symbols at the beginning of a subframe, a capacity of the PDCCH is restricted by the quantity of OFDM symbols that bear a control channel In addition, PDCCHs are dispersively mapped to frequency resources. As a result, it is difficult to avoid interference of PDCCHs between cells. Therefore, an R-PDCCH (Relay Physical Downlink Control Channel, relay physical downlink control channel) is introduced for a relay link between an eNB (evolved Node B, evolved base station) and a Relay (relay). The R-PDCCH may be mapped to a data area and uses, like a PDSCH (Physical Downlink Shared Channel, physical downlink shared channel), an FDM (Frequency-division multiplexing, Frequency-division multiplexing) manner to avoid the interference by occupying different frequency resources, that is, virtual resource blocks. Furthermore, because the quantity of Relay nodes is relatively small, a PUCCH format 1a or 1b (which may also be represented as PUCCH format 1a or 1b (PUCCH format 1a or 1b)) resource number corresponding to the R-PDCCH can be configured by using higher layer signaling.
However, in a scenario in which the quantity of UEs is relatively large, the PUCCH format 1a or 1b resource number is still configured by using the higher layer signaling. This results in a waste of resources and results in control signaling overhead.